1. Field of the Invention
This invention relates to a battery receiving chamber and a hearing aid using the same, and more particularly, is suitable to a waterproof type of hearing aid.
2. Description of the Related Art
Heretofore, in this type of hearing aid, a waterproof function has been attained by increasing a degree of tight-coupling between components.
As this type of hearing aid, there is an ear-hung type of hearing aid 1 (Japanese Patent Publication No. 3-39440 and Japanese Utility Model Publication No. 3-6075) as shown in FIG. 1. That is, in the hearing aid 1, a hook 3 is spring-coupled to an edge part of a case 2 formed in an arched shape as a whole, and the entire hearing aid 1 can be held at a backside position of user's earlobe by hanging the hook 3 on the upper end part of user's earlobe.
By attaching a tube and an ear plug (not shown) to an edge of the hook 3, the hearing aid 1 can send hearing aid sound, which is obtained from the earphone, into user's ear-hole through a sound path in the hook 3, the tube and ear plug.
A case 2 comprises a case itself 4, a case chassis 5, and a battery cover 7, and the case itself 4 internally includes a microphone, a processing circuit for hearing aid sound, an earphone, and the like. The case chassis 5 is pivotally joined to the case itself 4 by making a pivot (not shown), which is located at an end of the case itself 4, a rotation center. Therefore, in the hearing aid 1, each part built in the case itself 4 is adjusted and repaired after making the case chassis 5 open by rotating the case chassis 5 toward an arrow "a".
A battery cover 7 is pivotally joined to a base part of the case itself 4 by making a pivot 6 a rotation center. Thus, in the hearing aid 1, a battery is changed after making the battery cover 7 open by rotating the battery cover 7 toward an arrow "b".
A volume control knob 8 and a switch knob 9 for switching a power supply and various functions are disposed on a surface of the case chassis 5, and these parts are connected to each switch part built in the case itself 4 through each wire passing through thickness of the case chassis 5. Furthermore, an adjustment cover 10 protecting an adjustment part that adjusts a band of the hearing aid sound and a maximum sound pressure level is pivotally joined to the surface of the case chassis 5 by making a pivot 11 as a rotation center.
Here, in the hearing aid 1, moisture invasion from each joint surface is protected by using seal packings, which have shapes suitable to each of joint surfaces, at a joint surface of the case itself 4 and case chassis 5 and at a joint surface of the case itself 4 and battery cover 7.
O-rings are used respectively between the volume control knob 8 and case chassis 5, and between the switch knob 9 and case chassis 5. Therefore, these O-rings prevent the moisture invasion from a gap between the volume control knob 8 and case chassis 5, and another gap between the switch knob 9 and case chassis 5.
A wind cover 12 is provided at the edge part of the case 2 so as to prevent a wind noise from invading into the microphone, and the wind cover 12, which is embedded with the case 2, is held between the hook 3 and case 2 by screwing the hook 3 onto the case itself 4. That is, the hearing aid 1 introduces external sound to an external sound inlet of the microphone through a notch (not shown) formed nearby the hook 3 of the wind cover 12.
Here, a suitable waterproof component such as a filter that passes sound through but does not pass moisture through is located at the external sound inlet of the microphone so that the waterproof component prevents moisture invasion to the microphone. In this manner, the hearing aid 1 can prevent beforehand moisture invasion into the case 2 by adopting waterproof sealing between components.
Recently, environmental destruction by mercury in abandoned batteries gets much attention so that air cells such as zinc-air cells, which use oxygen in the air as polarity recovery agent, are investigated also in the hearing aid field.
Since the air cells have not actually environmental problems in comparison with the mercury cells and their electric capacity is large, it is also possible to sufficiently use the air cells as power supply cells for common hearing aids.
However, generally speaking, an inside of a waterproof type of hearing aid is hermetically formed, as above described, so as to realize a waterproof function. Therefore, it is difficult to apply above-described air cells, which need oxygen so as to generate voltages, as power supply cells for such hearing aids.
As a means to solve this issue, Japanese Patent Application No. 2-125464 proposes to form a battery cover of a hearing aid as shown in FIG. 2.
That is, in a hearing aid 20, a knob container 21A comprising concave parts in predetermined depth is provided in the center part of the upper surface of the battery cover 21, and a knob 22 is rotationally mounted in the knob container 21A. In addition, the knob 22 is connected to a lock mechanism located inside the battery cover 21.
Thus, the battery cover 21 can be locked so as not to be detached from a hearing aid itself 23 by rotating the knob 22 for containing itself in the knob container 21A in a state where the battery cover 21 is set to the hearing aid itself 23. On the other hand, the battery cover 21 can be detached from the hearing aid itself 23 after unlocking through rotating the knob 22 like protruding the knob 22 outward from the state where the knob 22 is contained in the knob container 21A.
In addition, on the lower face of the battery cover 21, a circular side wall 21B is protrudingly formed for retaining the external circumference of the battery 24 in the battery compartment 23A of the hearing aid itself 23. Furthermore, since an O-ring composed of elastic material such as rubber material is attached as surrounding a base part of the side wall 21B, the battery cover 21 can be set in high close-coupling degree to the hearing aid itself 23.
In this case, a through-hole (not shown) is formed at the bottom of the knob container 21A in the battery cover 21, a filter 25 that passes air through but does not pass moisture through (hereinafter: a waterproof filter) is located so as to block the through-hole. Therefore, when the battery cover 21 is set to the hearing aid itself 23, this hearing aid can supply air in the knob container 21A in the battery cover 21 through the waterproof filter 25 into the battery compartment 23A in the hearing aid itself 23.
Thus, since this hearing aid 20 can supply air into the battery compartment without degrading of a waterproof characteristic, the air cell can be used as a power supply cell.
However, this type of hearing aid 20 has a problem that the waterproof filter 25 is slow-drying because, as above described, the through-hole is formed at the bottom of the knob container 21A and the knob 22 covers the waterproof filter 25 in use.
In this case, the wet waterproof filter 25 hardly passes air so that this type of hearing aid has a problem that it cannot supply sufficient oxygen to the air cell contained in the battery compartment 23A in the hearing aid itself 23.
Here, in the hearing aid 1, as shown in FIG. 3, the above-described seal packing 20, which is inserted between the case itself 4 and battery cover 7, is formed in a rectangular shape suitable to the above-described joint part 4A composed of the lower part of the case itself 4 (and the above-described joint part 7A composed of the edge of the side wall of the battery cover 7). Therefore, the seal packing is embedded with a slot (not shown) located at the joint 7A of the battery cover 7 so that the water proof can be realized.
In addition, in this hearing aid 1, after closing the battery cover 7 by rotating it toward the closing direction shown by an arrow "c", by locking the battery cover 7 so as not to open through rotating a lock knob 21 toward the lock direction shown by an arrow "d", the joint part 4A of the case itself 4 and the joint part 7A of the battery cover 7 can pinch and hold the seal packing 20. Accordingly, it is possible to prevent the moisture invasion from between the joint part 4A of the case itself 4 and the joint part 7A of the battery cover 7 into the inside of the case 2.
However, in the hearing aid 1 having such a constitution, the seal packing 20 is formed in a rectangular shape so that strength of a pinching force at a corner of joints against the seal packing 20 that is located between the joint part 4A of the case itself 4 and the joint part 7A of the battery cover 7 is minutely different from that at a side of the joints in a locked state of the battery cover 7. Therefore, this type of hearing aid has a problem that external moisture easily invade from a part having weaker pinching force against the seal packing 20 among the joint part 4A of the case itself 4 and the joint part 7A of the battery cover 7.
Furthermore, according to an embedding method of the battery cover 7 with the case itself 4 by setting a rotating shaft 6 as a rotation center, there is a limitation of the pinching force against the seal packing 20. Thus, it is possible to prevent moisture invasion if water drops such as sweat pour on. However, it is difficult to obtain the pinching force necessary to enable the hearing aid 1 to have the waterproof characteristic for use in a swimming pool, bath compartment, and the like where the waterproof characteristic is necessary.
As one of means to solve these problems, it is possible to form the battery cover separately from the case itself and to use an O-ring for the waterproof structure.
Since an O-ring has no corner, uniform pressure along the circumference can be easily given to the O-ring even if one of various methods such as a press fit method is applied as a setting method of the battery cover to the case itself. Therefore, it is possible to obtain highly reliable waterproof performance by composing the battery receiving chamber of the hearing aid.
However, since a user of a hearing aid is usually an aged person who is clumsy, it is problem in view point of using convenience to detach the battery cover against the elastic force of the O-ring when detaching the battery cover from the case itself, if the press fit method is applied as a setting method of the battery cover of the battery receiving chamber to the case itself.
In the hearing aid 1 having such a constitution, as shown in FIG. 4, a microphone 20 and an earphone 21 are contained in an edge portion of the inside of the case itself 4. Therefore, the case chassis 5 is divided from the case 2 by two surfaces perpendicular to the back surface of the case 2 and a curved surface approximately parallel to the back surface of the case 2. In addition, the case chassis 5 forms from the back-end of the microphone 20 to near the battery cover 7 in the back surface of the case 2. Thus, a joint part 22 of the case itself 4 and case chassis 5 is formed with two surfaces 22A and 22B perpendicular to the back surface of the case 2 and a curved surface 22C approximately parallel to the back surface of the case 2.
Therefore, as shown in FIG. 5, a seal packing 23 that is inserted to a joint part 22 of the case itself 4 and case chassis 5 corresponds to the shape of the circumference edge face of the opening 24 formed in the back surface of the case itself 4. Consequently, the seal packing 23 is composed of curved parts 23A and 23B and a first and second bent parts 23C and 23D formed at both edges of the curved parts 23A and 23B.
In this manner, the hearing aid 1 is assembled as a whole, as shown in FIG. 1 by screwing the case chassis 5 onto a fixture 26 located inside the case itself 4 after embedding this seal packing 23 with a slot 25 formed in the circumference edge face of the opening 24 in the case itself 4. Therefore, the hearing aid 1 can prevent moisture invasion into the inside of the case 2 from the joint part 22 by sealing the joint part 22 of the case itself 4 and case chassis 5 with a seal packing 23.
However, in the hearing aid 1 having this type of constitution, it is a problem that stress to the seal packing 23 inserted to the joint part 22 is biased when the case chassis 5 is closed. Thus, in the hearing aid 1, the case chassis 5 and case itself 4 are connected so as to put stress perpendicularly onto the case itself 4 from the case chassis 5. Therefore, although the curved parts 23A and 23B of the seal packing 23 can obtain sufficient stress, the bent parts 23C and 23D of the seal packing 23 have possibility not to obtain sufficient stress. If it happens, the hearing aid 1 cannot seal the surfaces 22A and 22B perpendicular to the back surface of the case 2 in the joint part 22 of the case itself 4 and case chassis 5 so that the hearing aid 1 is not sufficient as a waterproof type of hearing aid.
In addition, since the hearing aid 1 has a constitution where both ends of the seal packing 23 are bent, assembling operation is difficult and shaping of the seal packing 23 itself is difficult, too.